It may not be quite on a par with the Manhattan Project or with the challenge of beating the Soviets to the moon, but the race to find a substitute for the lacquer used to line food cans is heating up.

The canning industry is frantically trying to find a replacement for the epoxy resin currently being used because of concerns that bisphenol A (BPA), a chemical that has been vilified as an “endocrine disruptor,” might be leaching into the contents. BPA is combined with other components to form a polymer that keeps the metal from reacting with the food. Once the BPA has been incorporated into the polymer, it no longer has any hormonal effects. But there are always traces of unreacted BPA left over that can indeed leach out.

Before exploring this issue, a bit of history is in order.

Napoleon, as with many other generals before him, discovered that soldiers do not fight well on empty stomachs. And stomachs were often empty due to the difficulty of supplying food to massive travelling armies. So the emperor offered a prize of 12,000 francs, a healthy amount of money at the time, to anyone who could come up with a viable method of preserving food.

This challenge was taken up by Nicolas Appert, who, as the son of an innkeeper, had learned about brewing and pickling. These “fermentation” method, he knew, could be halted by heat, and he began to wonder if food spoilage could also be stopped in this fashion. After all, it was clear that cooked food kept longer than fresh food, although eventually it too would spoil.

Years of experimentation led Appert to make a critical discovery: if the food were sealed in a glass jar and then heated, it would keep for a remarkably long time. Long enough, at any rate, to please Napoleon, who awarded the prize to Appert in 1809. For the method clearly worked, although nobody at the time understood why, since bacteria were not identified as the cause of food spoilage until another famous Frenchman, Louis Pasteur, came along later in the century.

Appert’s invention came to the attention of merchant Peter Durand in England, who was troubled by the use of glass jars, which often broke. There had to be a better way of storing food! Why not a metal container? Iron was cheap, and was his first choice. But iron corroded, especially when exposed to acidic foods. A coating that would protect it from the air and contents had to be found. Tin, concluded Durand, would do the job. The metal had been known since antiquity and could be easily melted and applied as a coating to iron, to make tin plate. And most importantly, tin did not corrode. By 1818, the British company Donkin and Hall was mass-producing food in tin cans.

When Admiral Parry sailed to the Arctic Circle in 1824, he sustained his crew on canned food. At least one can of roast veal apparently was not consumed, as just such a can turned up in a museum 114 years later. Inquisitive scientists opened it and decided to check the effectiveness of the canning process. They were not quite brave enough to try to eat the veal themselves, but the rats and cats who were given the pleasure of partaking of the 114-year-old feast not only survived — they thrived.

Although tin did not corrode, small amounts did dissolve, resulting in tainted food. Aluminum eventually turned out to be more suitable for cans, but aluminum still presented a problem of interacting with the food. As a result, chemists stepped into the picture and found that an epoxy resin made by reacting bisphenol A with epichlorohydrin was excellent in providing a barrier that was stable under the high heat and pressure of sterilization. What’s more, it did not crack if the can was dented, and stood up well to the varying acidity of different foods.

Epoxy resins performed admirably, but cracks, figuratively speaking, began to appear in the early-1990s. By then, analytical techniques had been developed to detect extremely small amounts of BPA. More importantly, the hormonal effects of this chemical were being demonstrated by its effects on the multiplication of cultured breast cancer cells. In 1995, researchers at the University of Granada in Spain investigated a number of canned foods and found estrogenic activity in peas, artichokes, green beans, corn and mushrooms — but not in asparagus, palm hearts, peppers or tomatoes. The authors pointed out that while an estrogenic effect was observed, it was far less than that observed for estradiol, the body’s naturally occurring estrogen.

The significance of the estrogenic effect of canned foods is difficult to estimate, given that on top of the estrogen produced by the body we are exposed to a wide variety of natural estrogenic compounds found in foods including milk, chickpeas, soybeans, vegetable oils, cabbage, flaxseeds and oats. It should also be noted that the concentration of pure bisphenol A required to produce maximum proliferation of breast cancer cells in the laboratory is 1,000-fold greater than for estradiol.

Though no risk from traces of BPA in canned foods has been demonstrated, there is a clamour for invoking the “precautionary principle” that aims to prevent harm even when the evidence is not fully in. For food companies, pleasing consumers is a high priority, whether demands are justified or not. So the race is on to find substitutes for epoxy resins.

In some cases, for such low-acid foods as beans, plant extracts that harden into a resin have met with success. For other foods, companies are looking into various acrylics, polyesters, polyurethanes and polyvinyl compounds. These do not match the performance of epoxy resin, nor is it clear that they have a better safety profile. Could we be trading in a perceived but unsubstantiated risk for a possible increased risk of food poisoning?

While you’ve been reading this column, hundreds of people have died from hunger, lack of clean water, poor sanitation and a host of preventable diseases ranging from malaria to AIDS. By contrast, we have the luxury of worrying about traces of chemicals contaminating our very ample food supply. A prescription for a dose of perspective is in order.

Joe Schwarcz is director of McGill University’s Office for Science & Society (www.mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.